The present invention is directed to an improved reverse-cycle heat pump system, and more specifically, to a reverse-cycle heat pump system comprising components that render the system more efficient in cooling during operation in the cooling mode.
Conventional reverse-cycle heat pump refrigeration systems comprise two reversible heat exchangers. One heat exchanger is placed in the space to be heated or cooled and the other heat exchanger is placed outside that space. In the heating mode, the inside heat exchanger functions as the condenser while the outside heat exchanger functions as the evaporator. In cooling mode, the roles are reversed (i.e. the inside heat exchanger functions as the evaporator and the outside heat exchanger functions as the condenser). The heat exchangers are connected to one another by a series of conduits or circuits through which refrigerant is pumped via a motorized compressor. A four-way valve is disposed within the series conduits and functions to direct the flow of refrigerant from the compressor to the appropriate heat exchanger. While the direction of refrigerant through the compressor always flows in one direction, the flow of refrigerant may change direction throughout the rest of the system depending upon whether the system is operating in the heating mode or cooling mode.
In heating mode, the compressor pumps hot, high-pressure refrigerant gas to the indoor heat exchanger, or "condenser," where the gas is condensed into a high pressure liquid as it gives off latent heat of condensation into the conditioned area. The high-pressure liquid then flows out of the condenser through a conduit or series of conduits and enters the outdoor exchanger, or "evaporator," as a low pressure liquid, wherein it absorbs latent heat from the outside and vaporizes. Low pressure refrigerant gas then exits the evaporator and returns to the compressor to begin the cycle again. Heating of the conditioned space is further aided by a fan positioned behind the condenser to blow heated air therein. A fan disposed behind the evaporator aids in drawing in heat from the outside into the system.
In cooling mode, the compressor pumps hot, high-pressure refrigerant gas in the reverse direction to the outdoor heat exchanger (i.e. "condenser") where the refrigerant gas is condensed into a high pressure liquid as it gives off latent heat of condensation to the outside. The resulting high-pressure refrigerant liquid then flows out of the condenser through a conduit or series of conduits and enters the indoor heat exchanger (i.e. "evaporator") wherein it absorbs latent heat from the area to be conditioned and consequently vaporizes. Cooling of the conditioned space is further aided by a fan positioned behind the evaporator to blow cooled air therein. A fan disposed behind the condenser aids in removing heat from the interior of the system.
A major disadvantage inherent in reverse cycle heat pumps is that the efficiency of the system in cooling mode is about 60% compared to that of the heating mode. The reason for this inefficiency is that it takes a much greater pressure drop on the condenser side of the system to dissipate the heat therefrom than it does to absorb heat from the evaporator side. Thus, in heating mode, a greater refrigerant charge is therefore necessary to heat a desired area; however, in the cooling mode, it is more difficult to dissipate the heat generated within the condenser to the outside, where temperatures are presumably already over 80.degree. F. Stated another way, there is generally more refrigerant within the system than needed to cool the inside air or water in a given area. Moreover, this higher refrigerant charge will tend to generate more heat within the heat pump system, thereby diminishing the cooling effect of the evaporator.
Prior art reverse cycle heat pump systems attempt to improve cooling mode efficiency by employing complex double heat exchangers with check valves. Such devices add a significant monetary cost to the product. It is therefore desirable to have a reverse-cycle heat pump system that accomplishes greater cooling efficiency in cooling mode without compromising the heating efficiency in heating mode, whereby the heat pump system employs components of minimal complexity and cost.